Seven speed dual clutch transmission

ABSTRACT

A transmission connectable to an input member and having an output transfer gear, first and second transmission input shaft members, first and second countershaft members, a plurality of co-planar gear sets, and a plurality of torque transmitting devices. The torque transmitting devices include a plurality of gears, synchronizer assemblies and a dual clutch assembly. The transmission is operable to provide at least one reverse speed ratio and a plurality of forward speed ratios between the input member and the output member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.61/179,905, filed on May 20, 2009, which is hereby incorporated in itsentirety herein by reference.

TECHNICAL FIELD

The present disclosure relates to transmissions and more particularly toa compact, dual clutch multiple speed transmission having at least threeaxes to establish seven or more gear speeds.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may or may not constitute priorart.

A typical multiple speed transmission having countershafts and co-planargear sets uses countershaft gears with a different, dedicated gear pairor set to achieve each forward speed ratio. Accordingly, the totalnumber of gears required in this typical design is two times the numberof forward speeds, plus three for reverse. This necessitates a largenumber of required gear pairs, especially in transmissions that have arelatively large number of forward speed ratios.

While current transmissions achieve their intended purpose, the need fornew and improved transmission configurations which exhibit improvedperformance, especially from the standpoints of efficiency,responsiveness and smoothness and improved packaging, primarily reducedsize and weight, is essentially constant. Accordingly, there is a needin the art for a transmission having improved packaging while providingdesirable gear ratios and torque ranges.

SUMMARY

The present invention provides a transmission coupled to an input memberand having an output member, first and second shaft members, first andsecond countershaft members, a park gear shaft, a plurality of co-planargear sets, and a plurality of torque transmitting devices. The torquetransmitting devices include a plurality of gears, synchronizerassemblies and a dual clutch assembly. The transmission is operable toprovide at least one reverse speed ratio and a plurality of forwardspeed ratios between the input member and the output member.

In one aspect of the present invention, the transmission includes atransmission housing.

In another aspect of the present invention, the transmission includes adual clutch assembly having a first clutch, second clutch, and a clutchhousing connectable to an engine output member. The clutch housing isrotationally supported within the transmission housing.

In another aspect of the present invention, the transmission includes afirst, second, third, fourth and fifth gear set. The first gear setincludes a first gear in mesh with a second gear and a third gear inmesh with the second gear, the second gear set includes a first gear inmesh with a second gear and a third gear, the third gear set includes afirst gear in mesh with a second gear and a third gear, the fourth gearset includes a first gear in mesh with a second gear, the fifth gear setincludes a first gear in mesh with a second gear. The second gear of thefifth gear set is a stepped pinion gear having a first and a second gearteeth portions, and wherein the first gear teeth portion is larger thanthe second gear teeth portion and meshes with the first gear of thefifth gear set.

In another aspect of the present invention, the transmission includes afirst transmission input member rotatably supported in the transmissionhousing. Each of the first gears of the third, fourth and fifth gearsets are rotatably fixed for common rotation with the first transmissioninput member. The selective engagement of the first clutch of the dualclutch assembly transfers torque form the clutch housing to the firsttransmission input member.

In another aspect of the present invention, the transmission includessecond transmission input member rotatably supported in the transmissionhousing. Each of the first gears of the first and second gear sets arerotatably fixed for common rotation with the second transmission inputmember. The second transmission input member is concentric with thefirst transmission input member and at least partially surrounds thefirst transmission input member. The selective engagement of the secondclutch of the dual clutch assembly transfers torque form the clutchhousing to the second transmission input member.

In another aspect of the present invention, the transmission includes afirst countershaft rotatably supported within the transmission housingand spaced apart from and parallel with the first and secondtransmission input members. The third gear of the first gear set, thethird gear of the second gear set, the third gear of the third gear setand the second gear of the fourth gear set are each selectivelyconnectable for common rotation with the first countershaft.

In another aspect of the present invention, the transmission includes asecond countershaft rotatably supported within the transmission housingand spaced apart from and parallel with the first and secondtransmission input members. The second gear of the first gear set, thesecond gear of the second gear set, the second gear of the third gearset and the second gear of the fifth gear set are each selectivelyconnectable for common rotation with the second countershaft.

In another aspect of the present invention, the transmission includes afirst synchronizer assembly selectively connects at least one of thesecond gear of the first gear set and the second gear of the second gearset to the second countershaft.

In another aspect of the present invention, the transmission includes asecond synchronizer assembly selectively connects at least one of thethird gear of the first gear set and third gear of the second gear setto the first countershaft.

In another aspect of the present invention, the transmission includes athird synchronizer assembly selectively connects at least one of thesecond gear of the third gear set and the second gear teeth portion ofthe second gear of the fifth gear set to the second countershaft.

In another aspect of the present invention, the transmission includes afourth synchronizer assembly selectively connects at least one of thethird gear of the third gear set and the second gear of the fourth gearset to the first countershaft.

In another aspect of the present invention, the transmission includes afirst countershaft transfer gear fixed to the first countershaft forcommon rotation with the first countershaft and a second countershafttransfer gear fixed to the second countershaft for common rotation withthe second countershaft and wherein the first and second countershafttransfer gears transfer torque from at least one of the first and secondcountershafts to a transmission output member.

In another aspect of the present invention, the transmission includes apark gear fixed to a first end of a park gear shaft and a park transfergear fixed to a second end of the park gear shaft. The park transfergear meshes with the transmission output member. The park gear isconfigured to prevent rotation of the transmission output member whenthe park gear is engaged.

In another aspect of the present invention, the selective engagement ofthe first and second clutches of the dual clutch assembly and theselective engagement of at least one of the synchronizer assembliesestablishes at least one of seven forward speed ratios between the atleast one of the first and the second transmission input members and thetransmission output member.

The above features and advantages and other features and advantages ofthe present invention are readily apparent from the following detaileddescription of the best modes for carrying out the invention when takenin connection with the accompanying drawings wherein like referencenumbers refer to the same component, element or feature.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic view of an embodiment of a seven speedtransmission having a park gear mounted on a separate park shaft, inaccordance with the present invention.

DESCRIPTION

Referring to FIG. 1, a multiple speed transmission is generallyindicated by reference number 10. The transmission 10 is coupled to aninput member 12 and includes an output member or gear 14. In the presentembodiment, the input member 12 is a shaft and the output member 14 is agear, however those skilled in the art will appreciate that the inputmember 12 may be components other than shafts and the output member 14may be a component, such as a shaft, other than a gear.

The input member 12 is continuously connected with an engine (not shown)or other torque producing machine to provide a driving torque to inputmember 12. The output member or gear 14 rotatably drives a differentialassembly 16. The differential assembly 16 transfers torque delivered byoutput member 14, ultimately, to a pair road wheels (not shown).

The transmission 10 includes a housing 18 that at least partiallyencloses a gearing arrangement 20. The gearing arrangement 20 includesvarious shafts or members, co-planar intermeshing gear sets, a dualclutch assembly, and selectively engageable synchronizers, as will bedescribed herein. For example, the gearing arrangement 20 includes afirst transmission input shaft or member 22, a second transmission inputshaft or member 24, a first countershaft 26, a second countershaft 28and park gear shaft 30. The second transmission input shaft or member 24is a sleeve (hollow) shaft that is concentric with and overlies thefirst transmission input shaft or member 22. The first countershaft 26,the second countershaft 28 and the park gear shaft 30 are each spacedapart from and parallel with the first and second transmission inputshaft members 22, 24. The first and second transmission input shafts 22,24 define a first axis of rotation, the first countershaft 26 defines asecond axis of rotation and the second countershaft 28 defines a thirdaxis of rotation. The position and location of countershafts 26 and 28relative to first and second transmission input shafts 22, 24 areinterchangeable.

A dual clutch assembly 32 is connected between the input member 12 andthe first and second transmission input shaft members 22, 24. The dualclutch assembly 32 includes a clutch housing 34 connectable for commonrotation with the input member 12. Further, the dual clutch assembly 32has first and second clutch elements or hubs 36 and 38. Clutch elements36 and 38 together with the clutch housing 34 are configured to form afriction clutch, as is known in the art as a dual clutch. Morespecifically, clutch elements 36, 38 and the clutch housing 34 havefriction plates mounted thereon or otherwise coupled thereto thatinteract to form a friction clutch. The clutch element 36 is connectedfor common rotation with the first transmission input shaft or member 22and the clutch element 38 is connected for common rotation with thesecond transmission input shaft or member 24. Thus, selective engagementof clutch element 36 with the clutch housing 34 connects the inputmember 12 for common rotation with the first transmission input shaftmember 22. Selective engagement of clutch element 38 with the clutchhousing 34 connects the input member 12 for common rotation with thesecond transmission input shaft member 24. In FIG. 1, the dual clutchassembly 32 is shown as dry clutch assembly. However, it should beappreciated that the dual clutch assembly 32 can be a wet clutchassembly without departing from the scope of the present invention.

The gearing arrangement 20 also includes a plurality of co-planar,meshing gear sets 40, 50, 60, 70 and 80. The present inventioncontemplates that the plurality of co-planar, meshing gear sets 40, 50,60, 70 and 80 may be arranged axially along transmission input shafts22, 24 in an order other than that which is shown in FIG. 1 and still bewithin the scope of the invention. Co-planar gear set 40 includes pinion42, gear 44, and gear 46. Pinion 42 is rotatably fixed and connected forcommon rotation with the second transmission input shaft member 24. Gear44 is selectively connectable for common rotation with the secondcountershaft member 28 and meshes with pinion 42. Gear 46 is selectivelyconnectable for common rotation with the first countershaft member 26and meshes with gear 44. It should be appreciated that pinion 42 may bea separate gear structure fixed to the second transmission input shaftmember 24 or gear teeth/splines formed on an outer surface of the secondtransmission input shaft member 24 without departing from the scope ofthe present invention. Gear set 40 is disposed proximate a wall 48 ofthe transmission housing 18 that is on a front or side of thetransmission 10 proximate the dual clutch assembly 32.

Co-planar gear set 50 includes pinion 52, gear 54 and gear 56. Pinion 52is rotatably fixed and connected for common rotation with the secondtransmission input shaft member 24 and meshes with gear 54 and gear 56.Gear 54 is selectively connectable for common rotation with the secondcountershaft member 28. Gear 56 is selectively connectable for commonrotation with the first countershaft member 26. Gear set 50 ispositioned adjacent gear set 40.

Co-planar gear set 60 includes pinion 62, gear 64 and gear 66. Pinion 62is rotatably fixed and connected for common rotation with the firsttransmission input shaft member 22 and meshes with gear 64 and gear 66.Gear 64 is selectively connectable for common rotation with the secondcountershaft member 28. Gear 66 is selectively connectable for commonrotation with the first countershaft member 26. Gear set 60 is disposedadjacent gear set 50.

Co-planar gear set 70 includes pinion 72 and gear 74. Pinion 72 isrotatably fixed and connected for common rotation with the firsttransmission input shaft member 22 and meshes with gear 74. Gear 74 isselectively connectable for common rotation with the first countershaftmember 26. Gear set 70 is positioned adjacent gear set 60.

Co-planar gear set 80 includes pinion 82 and gear 84. Pinion 82 isrotatably fixed and connected for common rotation with the firsttransmission input shaft member 22 and meshes with gear 84. Gear 84 isselectively connectable for common rotation with the second countershaftmember 28. Gear 84 includes a secondary or extension portion 84A that iskinematically connected to and fixed for common rotation with gear 84.Gear set 80 is positioned between gear set 70 and an end wall 88 of thetransmission housing 18.

Further, a first countershaft transfer gear 100 is rotatably fixed andconnected for common rotation with the first countershaft member 26. Asecond countershaft transfer gear 110 is rotatably fixed and connectedfor common rotation with the second countershaft member 28. A parktransfer gear 111 is rotatably fixed and connected for common rotationwith the park gear shaft 30. First countershaft transfer gear 100 isconfigured to mesh with output member 14, the second countershafttransfer gear 110 is configured to mesh with output member 14 and parktransfer gear 111 is configured to mesh with output member 14. However,the first countershaft transfer gear 100, the second countershafttransfer gear 110 and the park transfer gear 111 do not mesh with eachother. The first countershaft transfer gear 100 is disposed betweenco-planar gear set 40 and end wall 48 of the transmission housing 18.The second countershaft transfer gear 110 is also disposed betweenco-planar gear set 40 and end wall 48 of the transmission housing 18.The park transfer gear 111 is disposed proximate to wall 48 oftransmission housing 18 and co-planar with output gear or member 14.Moreover, the output member 14 is co-planar with first and secondcountershaft transfer gears 100, 110.

A park gear 112 is provided for placing transmission 10 in a park modethat prevents output member 14 from rotating. Park gear 112 is coupledto park transfer gear 111 through park gear shaft 30. Alternatively, thepresent invention contemplates fixedly disposing park gear 112 on one ofthe first and second countershafts 26, 28 to achieve the park modefunction. In this embodiment, the park transfer gear 111 and park gearshaft 30 are eliminated further improving packaging capability of thetransmission. Moreover, the axial location of park gear 112 along thecountershafts 26 or 28 may be changed in accordance with availablepackaging space.

With continued reference to FIG. 1, the transmission 10 further includesa plurality of selectively engageable synchronizer assemblies 150, 152,154 and 156. Synchronizers 150, 152, 154 and 156 are double sidedsynchronizers and generally include a shift fork (not shown) that isbi-directionally translated by an actuator (not shown) into at least twoengaged positions and a neutral or disengaged position. In the presentembodiment, synchronizer 150 is selectively actuatable to connect gear44 for common rotation with the second countershaft member 28 and isselectively actuatable to connect gear 54 for common rotation with thesecond countershaft member 28. Synchronizer 152 is selectivelyactuatable to connect for common rotation gear 46 with the firstcountershaft member 26 and is selectively actuatable to connect forcommon rotation gear 56 with the first countershaft member 26.Synchronizer 154 is selectively actuatable to connect for commonrotation gear 64 with the second countershaft 28 and is selectivelyactuatable to connect for common rotation gear extension portion 84A ofgear 84 with the second countershaft member 28. Synchronizer 156 isselectively actuatable to connect for common rotation gear 66 with thefirst countershaft member 26 and is selectively actuatable to connectfor common rotation gear 74 with the first countershaft member 26.

The transmission 10 is capable of transmitting torque from the inputshaft 12 to the output gear member 14 in at least seven forward torqueratios and at least one reverse torque ratio. Each of the forward torqueratios and the reverse torque ratio is attained by selective engagementof the dual clutch assembly 32 and one or more of the synchronizerassemblies 150, 152, 154 and 156. Those skilled in the art will readilyunderstand that a different speed ratio is associated with each torqueratio.

It should be appreciated that each individual gear set 40, 50, 60, 70and 80 provides one or more forward and/or reverse gear ratios uponselective engagement of the synchronizer assemblies 150, 152, 154 and156. It should also be appreciated that a particular forward or reversespeed ratio may be achieved by different combinations of synchronizerand associated gear sets without departing from the scope of the presentinvention.

For example, to establish the reverse torque ratio, clutch element 38 isengaged and synchronizer 152 is activated. Clutch element 38 couples theinput member 12 with the second transmission input shaft member 24.Synchronizer 152 connects gear 46 to the first countershaft member 26.More specifically, input torque from the input shaft 12 is transferredthrough the dual clutch assembly 32 to the second transmission inputshaft member 24, through pinion 42 to gear 44, through gear 44 to gear46, from gear 46 to the first countershaft member 26 throughsynchronizer 152 to first countershaft transfer gear 100 and from firstcountershaft transfer gear 100 to the output member 14.

To establish a first forward torque ratio (i.e. a 1st gear), clutchelement 36 is engaged and synchronizer 156 is activated. Clutch element36 couples the input member 12 with the first transmission input shaftmember 22. Synchronizer 156 couples gear 74 to the first countershaftmember 26. Input torque from the input member 12 is transferred throughthe dual clutch assembly 32 to the first transmission input shaft member22 to pinion 72. Pinion 72 transfers torque to gear 74 which transfersthe torque to the first countershaft member 26 through synchronizer 156and to first countershaft transfer gear 100 and then from firstcountershaft transfer gear 100 to the output member 14.

To establish a second forward torque ratio (i.e. a 2nd gear), clutchelement 38 is engaged and synchronizer 150 is activated. Clutch element38 couples the input member 12 to the second transmission input shaftmember 24 which rotates pinion 42. Synchronizer 150 couples gear 44 tothe second countershaft member 28. Accordingly, input torque from theinput member 12 is transferred through the dual clutch assembly 32 tothe second transmission input shaft member 24, through pinion 42 to gear44, from gear 44 to synchronizer 150, from synchronizer 150 to thesecond countershaft member 28 and from the second countershaft member 28to the second countershaft transfer gear 110 and the output member 14.

To establish a third forward torque ratio (i.e. a 3rd gear), clutchelement 36 is engaged and synchronizer 156 is activated. Clutch element36 couples the input member 12 to the first transmission input shaftmember 22 which rotates pinion 62. Synchronizer 156 couples gear 66 tothe first countershaft member 26. Thus, input torque from the inputmember 12 is transferred through the dual clutch assembly 32 to thefirst transmission input shaft member 22, through pinion 62 to gear 66,through gear 66 to synchronizer 156, from synchronizer 156 to the firstcountershaft member 26, from the first countershaft member 26 to thefirst countershaft transfer gear 100 and then from first countershafttransfer gear 100 to the output member 14.

To establish a fourth forward torque ratio (i.e. a 4th gear), clutchelement 38 is engaged and synchronizer 152 is activated. Clutch element38 couples the input member 12 to the second transmission input shaftmember 24 which rotates pinion 52. Synchronizer 152 couples gear 56 tothe first countershaft member 26. Thus, input torque from the inputmember 12 is transferred through the dual clutch assembly 32 to thesecond transmission input shaft member 24 to pinion 52, then from pinion52 to gear 56, from gear 56 to synchronizer 152, from synchronizer 152to the first countershaft member 26, from the first countershaft member26 to first countershaft transfer gear 100 and then from firstcountershaft transfer gear 100 to the output member 14.

To establish a fifth forward torque ratio (i.e. a 5th gear), clutchelement 36 is engaged and synchronizer 154 is activated. Clutch element36 couples the input member 12 to the first transmission input shaftmember 22 which rotates pinion 62. Synchronizer 154 couples gear 64 tothe second countershaft member 28. Input torque from the input member 12is transferred through the dual clutch assembly 32 to the firsttransmission input shaft member 22, from first transmission input shaftmember 22 to pinion 62, from pinion 62 to gear 64, from gear 64 to thesecond countershaft member 28 through synchronizer 154 to secondcountershaft transfer gear 110 and from second countershaft transfergear 110 to the output member 14.

To establish a sixth forward torque ratio (i.e. a 6th gear), clutchelement 38 is engaged and synchronizer 150 is activated. Clutch element38 couples the input member 12 to the second transmission input shaftmember 24 which rotates pinion 52. Synchronizer 150 couples gear 54 tothe second countershaft member 28. Thus, input torque from the inputmember 12 is transferred through the dual clutch assembly 32 to thesecond transmission input shaft member 24 to pinion 52, then from pinion52 to gear 54, from gear 54 to synchronizer 150, from synchronizer 150to the second countershaft member 28, from the second countershaftmember 28 to second countershaft transfer gear 110 and then from secondcountershaft transfer gear 110 to the output member 14.

To establish a seventh forward torque ratio (i.e. a 7th gear), clutchelement 36 is engaged and synchronizer 154 is activated. Clutch element36 couples the input member 12 to the first transmission input shaftmember 22 which rotates pinion 62. Synchronizer 154 couples gear 84 viaextending portion 84A to the second countershaft member 28. Input torquefrom the input member 12 is transferred through the dual clutch assembly32 to the first transmission input shaft member 22, from firsttransmission input shaft member 22 to pinion 82, from pinion 82 to gear84, from gear 84 to the second countershaft member 28 throughsynchronizer 154 to second countershaft transfer gear 110 and fromsecond countershaft transfer gear 110 to the output member 14.

Again, it should be appreciated that any one of the gear sets of gearsets 40, 50, 60, 70 and 80 may be changed to produce a certain forwardand reverse torque ratio without departing from the scope of the presentinvention.

The present invention contemplates that a variety of torque ratios(i.e., the ratio of torque of the output member 14 to the input member12) and ratio steps are achievable through the selection of tooth countsof the gears of the transmission 10. The present invention has manyadvantages and benefits over the prior art. For example, the utilizationof four synchronizers allows the use of four rails having one fork oneach rail. Thus, a transmission having a more simplified actuation andcontrol system, reduced mass and cost and improved packaging isachieved.

While the best modes for carrying out the invention have been describedin detail, those familiar with the art to which this invention relateswill recognize various alternative designs and embodiments forpracticing the invention within the scope of the appended claims.

1. A transmission comprising: a transmission housing; a dual clutchassembly having a first clutch, second clutch, and a clutch housingconnectable to an engine output member, wherein the clutch housing isrotationally supported within the transmission housing; a first, second,third, fourth and fifth gear set, wherein the first gear set includes afirst gear in mesh with a second gear and a third gear in mesh with thesecond gear, the second gear set includes a first gear in mesh with asecond gear and a third gear, the third gear set includes a first gearin mesh with a second gear and a third gear, the fourth gear setincludes a first gear in mesh with a second gear, the fifth gear setincludes a first gear in mesh with a second gear, wherein the secondgear of the fifth gear set is a stepped pinion gear having a first and asecond gear teeth portions, and wherein the first gear teeth portion islarger than the second gear teeth portion and meshes with the first gearof the fifth gear set; a first transmission input member rotatablysupported in the transmission housing, and wherein each of the firstgears of the third, fourth and fifth gear sets are rotatably fixed forcommon rotation with the first transmission input member, wherein theselective engagement of the first clutch of the dual clutch assemblytransfers torque form the clutch housing to the first transmission inputmember; a second transmission input member rotatably supported in thetransmission housing and, wherein each of the first gears of the firstand second gear sets are rotatably fixed for common rotation with thesecond transmission input member and wherein the second transmissioninput member is concentric with the first transmission input member andat least partially surrounds the first transmission input member, andwherein the selective engagement of the second clutch of the dual clutchassembly transfers torque form the clutch housing to the secondtransmission input member; a first countershaft rotatably supportedwithin the transmission housing and spaced apart from and parallel withthe first and second transmission input members, wherein the third gearof the first gear set, the third gear of the second gear set, the thirdgear of the third gear set and the second gear of the fourth gear setare each selectively connectable for common rotation with the firstcountershaft; a second countershaft rotatably supported within thetransmission housing and spaced apart from and parallel with the firstand second transmission input members, wherein the second gear of thefirst gear set, the second gear of the second gear set, the second gearof the third gear set and the second gear of the fifth gear set are eachselectively connectable for common rotation with the secondcountershaft; and four synchronizer assemblies for selectively couplingat least one of the gears of the first, second, third, fourth and fifthgear sets with at least one of the first countershaft and the secondcountershaft, and wherein the selective engagement of dual clutchassembly interconnects the dual clutch housing with at least one of thefirst and the second transmission input members and the selectiveengagement of at least one of the four synchronizer assembliesestablishes at least one of seven forward speed ratios.
 2. Thetransmission of claim 1 wherein a first of the four synchronizerassemblies selectively connects at least one of the second gear of thefirst gear set and the second gear of the second gear set to the secondcountershaft.
 3. The transmission of claim 2 wherein a second of thefour synchronizer assemblies selectively connects at least one of thethird gear of the first gear set and third gear of the second gear setto the first countershaft.
 4. The transmission of claim 3 wherein athird of the four synchronizer assemblies selectively connects at leastone of the second gear of the third gear set and the second gear teethportion of the second gear of the fifth gear set to the secondcountershaft.
 5. The transmission of claim 4 wherein a fourth of thefour synchronizer assemblies selectively connects at least one of thethird gear of the third gear set and the second gear of the fourth gearset to the first countershaft.
 6. The transmission of claim 1 whereinthe first gear set is adjacent the dual clutch assembly, the second gearset is adjacent the first gear set, the third gear set is adjacent thesecond gear set, the fourth gear set is adjacent the third gear set, andthe fifth gear set is adjacent the fourth gear set.
 7. The transmissionof claim 6 wherein the four synchronizer assemblies includes a firstsynchronizer assembly for selectively connecting the second gear of thefirst gear set to the second countershaft to establish a second gearratio when the second clutch of the dual clutch is engaged to connectthe dual clutch housing to the second transmission input member.
 8. Thetransmission of claim 6 wherein the four synchronizer assembliesincludes a first synchronizer assembly for selectively connecting thesecond gear of the second gear set to the second countershaft toestablish a sixth gear ratio when the second clutch of the dual clutchis engaged to connect the dual clutch housing to the second transmissioninput member.
 9. The transmission of claim 6 wherein the foursynchronizer assemblies includes a second synchronizer assembly forselectively connecting the third gear of the first gear set to the firstcountershaft to establish a reverse gear ratio when the second clutch ofthe dual clutch is engaged to connect the dual clutch housing to thesecond transmission input member.
 10. The transmission of claim 6wherein the four synchronizer assemblies includes a second synchronizerassembly for selectively connecting the third gear of the second gearset to the first countershaft to establish a fourth gear ratio when thesecond clutch of the dual clutch is engaged to connect the dual clutchhousing to the second transmission input member.
 11. The transmission ofclaim 6 wherein the four synchronizer assemblies includes a thirdsynchronizer assembly for selectively connecting the second gear of thethird gear set to the second countershaft to establish a fifth gearratio when the first clutch of the dual clutch is engaged to connect thedual clutch housing to the first transmission input member.
 12. Thetransmission of claim 6 wherein the four synchronizer assembliesincludes a third synchronizer assembly for selectively connecting thesecond gear teeth portion of the second gear of the fifth gear set tothe second countershaft to establish a seventh gear ratio when the firstclutch of the dual clutch is engaged to connect the dual clutch housingto the first transmission input member.
 13. The transmission of claim 6wherein the four synchronizer assemblies includes a fourth synchronizerassembly for selectively connecting the third gear of the third gear setto the first countershaft to establish a third gear ratio when thesecond clutch of the dual clutch is engaged to connect the dual clutchhousing to the second transmission input member.
 14. The transmission ofclaim 6 wherein the four synchronizer assemblies includes a fourthsynchronizer assembly for selectively connecting the second gear of thefourth gear set to the first countershaft to establish a first gearratio when the first clutch of the dual clutch is engaged to connect thedual clutch housing to the first transmission input member.
 15. Thetransmission of claim 1 further comprising a first countershaft transfergear fixed to the first countershaft for common rotation with the firstcountershaft and a second countershaft transfer gear fixed to the secondcountershaft for common rotation with the second countershaft andwherein the first and second countershaft transfer gears transfer torquefrom at least one of the first and second countershafts to atransmission output member.
 16. The transmission of claim 15 wherein thetransmission output member is a gear that meshes with the each of thefirst and second countershaft transfer gears.
 17. The transmission ofclaim 15 further comprising a park gear fixed to a first end of a parkgear shaft and a park transfer gear fixed to a second end of the parkgear shaft and wherein the park transfer gear meshes with thetransmission output member and wherein the park gear is configured toprevent rotation of the transmission output member when the park gear isengaged.
 18. A transmission comprising: a transmission housing; a dualclutch assembly having a first clutch, second clutch, and a clutchhousing connectable to an engine output member, wherein the clutchhousing is rotationally supported within the transmission housing; afirst, second, third, fourth and fifth gear set, wherein the first gearset includes a first gear in mesh with a second gear and a third gear inmesh with the second gear, the second gear set includes a first gear inmesh with a second gear and a third gear, the third gear set includes afirst gear in mesh with a second gear and a third gear, the fourth gearset includes a first gear in mesh with a second gear, the fifth gear setincludes a first gear in mesh with a second gear, wherein the secondgear of the fifth gear set is a stepped pinion gear having a first and asecond gear teeth portions, and wherein the first gear teeth portion islarger than the second gear teeth portion and meshes with the first gearof the fifth gear set; a first transmission input member rotatablysupported in the transmission housing, and wherein each of the firstgears of the third, fourth and fifth gear sets are rotatably fixed forcommon rotation with the first transmission input member, wherein theselective engagement of the first clutch of the dual clutch assemblytransfers torque form the clutch housing to the first transmission inputmember; a second transmission input member rotatably supported in thetransmission housing and, wherein each of the first gears of the firstand second gear sets are rotatably fixed for common rotation with thesecond transmission input member and wherein the second transmissioninput member is concentric with the first transmission input member andat least partially surrounds the first transmission input member, andwherein the selective engagement of the second clutch of the dual clutchassembly transfers torque form the clutch housing to the secondtransmission input member; a first countershaft rotatably supportedwithin the transmission housing and spaced apart from and parallel withthe first and second transmission input members, wherein the third gearof the first gear set, the third gear of the second gear set, the thirdgear of the third gear set and the second gear of the fourth gear setare each selectively connectable for common rotation with the firstcountershaft; a second countershaft rotatably supported within thetransmission housing and spaced apart from and parallel with the firstand second transmission input members, wherein the second gear of thefirst gear set, the second gear of the second gear set, the second gearof the third gear set and the second gear of the fifth gear set are eachselectively connectable for common rotation with the secondcountershaft; a first synchronizer assembly selectively connects atleast one of the second gear of the first gear set and the second gearof the second gear set to the second countershaft; a second synchronizerassembly selectively connects at least one of the third gear of thefirst gear set and third gear of the second gear set to the firstcountershaft; a third synchronizer assembly selectively connects atleast one of the second gear of the third gear set and the second gearteeth portion of the second gear of the fifth gear set to the secondcountershaft; a fourth synchronizer assembly selectively connects atleast one of the third gear of the third gear set and the second gear ofthe fourth gear set to the first countershaft; a first countershafttransfer gear fixed to the first countershaft for common rotation withthe first countershaft and a second countershaft transfer gear fixed tothe second countershaft for common rotation with the second countershaftand wherein the first and second countershaft transfer gears transfertorque from at least one of the first and second countershafts to atransmission output member; and a park gear fixed to a first end of apark gear shaft and a park transfer gear fixed to a second end of thepark gear shaft and wherein the park transfer gear meshes with thetransmission output member and wherein the park gear is configured toprevent rotation of the transmission output member when the park gear isengaged, and wherein the selective engagement of the first and secondclutches of the dual clutch assembly and the selective engagement of atleast one of the synchronizer assemblies establishes at least one ofseven forward speed ratios between the at least one of the first and thesecond transmission input members and the transmission output member.